Method for advancing a continuously cast ingot along a curved withdrawal path

ABSTRACT

A continuously cast curved ingot is withdrawn from the mold by forces distributed so that one-tenth to one half of the total forces act on the upper side along the inside of the curved withdrawal path, the remaining forces act from below along the outer path.

[ 1 Dec,26,1972

United States Patent Vogt m N m MA .IP uT mA IT 8 D E W N U U .D

[54] METHOD FOR ADVANCING A CONTINUOUSLY CAST INGOT ALONG A CURVED WITHDRAWA L PATH 164/282 X 64/282 X ...l64/282 64/282 X 8/1960 Schneckenburger et al. ....l64/282 X W "t u "H mm? u at ud 08h mmkm OBMR 6790 6667 9999 III] l/l/ 2651 i 1 5 08 7437 1 ,32 70462 49244 ,5 i 23333 a m m l I n u a a. m n e k G My n m m m H S HG n I. a M mo 0 V e 0 nm r. BS 8 U G MD mym e t n n g e m V S .m A 1 2 3 7 7 rl rt [22] Filed: Jan. 20, 1971 [21] App]. No.: 108,003

Primary Examiner-R. Spencer Annear Attorney-Smyth, Roston & Pavitt [57] ABSTRACT A continuously cast curved ingot is withdrawn from the mold by forces distributed so that one-tenth to one [30] Foreign Application Priority Data Jan. 29, 1970 Germany.....................P 20 04 763.6

half of the total forces act on the upper side along the inside of the curved withdrawal path, the remaining forces act from below along the outer path.

22 H Q1 4 1, m u 4 6" 1m L." u QML Um 21 55 [58] Field of Search.........................164/82, 282, 283

5 Claims, 1 Drawing Figure 000 oQeQe l0 II METHOD FOR ADVANCING A CONTINUOUSLY CAST INGOT ALONG A CURVED WITHDRAWAL PATH The present invention relates to method for controlled withdrawal of a continuously cast steel ingot to be guided along a curved path by means of several driven support and guiding roll's. As is well known, the withdrawal of a continuously cast, steel ingot from a curved casting mold requires considerable forces, particularly if the dimensions of the ingot are rather large. ln accordance with German Pat. No. 1,250,973 it is known to-withdraw the ingot from curved, continuously casting equipment by means of driven support and guide rolls which are provided in addition to the usual transport rolls. Thisis particularly true for the withdrawal ,of ingots with a still liquidous core as the usual case.

One can see the problem if one' considers that, on one hand, considerable contact pressure forces are required for the rolls to develop traction to be enabled to importtheir torque as driving force upon the ingot; on the other hand, if the contact pressure forces as applied to and reached into the ingot are tooslarge, the skin or shell of the ingot may be damaged, even ruptured. Therefore, in order to avoid local concentration of applied contact pressure forces, the number of driven rolls is quite large. If all or many of these rolls as provided on both sides of the extracted ingot are driven, the equipment is necessarily very expensive. Therefore, in order to limit expenditure, casting equipment that has actually been built had many driven support rolls only where engaging the bottom of the cast and withdrawn ingot as it veers from the vertical to a horizontal direction of progression. That method, however, has the disadvantage that the solidified skin of the ingot is not uniformly subjected to driving and pulling forces, nor is the contact pressure uniformly applied, the lower side is more strongly under contact pressure than the upper side.

In accordance with German printed Patent application No. 1,902,117 and German Pat. No. 1,187,753 it has been suggested for other reasons to provide particular relationship between the several rolls as far as torque is concerned or to organize the several rolls into groups and to determine the torque as to the several groups of rolls. In accordance with the British Pat. No. 941,290 it has been suggested to drive some of the rolls along the outer (lower) path of a curved ingot faster than on the inside, but neither any division or particular organization of torque and applied forces as to the two different sides of the ingot is mentioned in that patent nor does that patent disclose any rule concerning the advance of the rolls that are to be driven faster.

The invention particularly is based on the afore-mentioned state of the art, and the problem solved is to particularly distribute the drive forces for the ingot on both sides for extracting same from the mold under consideration that the withdrawn ingot has a still liquidous core. The forces are to be applied upon the withdrawn ingot as uniform as possible as they are effective in the solidifying and solidified cross section. It is a particular object of the invention to set forth rules concerning minimization of the forces that are to be so applied.

In accordance with one aspect of the present invention and in the preferred embodiment thereof, it is suggested to withdraw a continuously cast ingot from a curved mold on a curved withdrawal path by means of driven support and guide rolls in such a manner that the ingot drive forces are distributed so that the sum of the total drive forces imparted upon the ingot by means of driven rolls on top of the ingot as veered from about vertical to a horizontal withdrawal path is one-tenth to one half of the sum of the drive forces as imparted by driven rolls upon the lower side of the withdrawn ingot. A particular device for practicing the method is characterized by inclusion of a driven roll on the inside of thecurved withdrawal path but before the first bending point.

The calculation of the required forces to be imparted upon such an ingot as a whole for its withdrawal from the mold, is known per se and is not subject of this invention. The invention is related to the distribution of these forces as they are provided by the individual rolls. The calculation of that distribution is preferably based on the'condition that an individual roll provides contact pressure force, for the transmission of a particular torque, corresponding to the 1to 1.5-fold value of the load on the roll by operation of the ferro-static pressure in the ingot. The calculation then leads to the total amount of the rolls that are to be driven on basis of the general rule as stated above.

While the specification concludes with claims particularly pointing out and distinctly claiming the subject matter which is regarded as the invention, it is believed that the invention, the objects and features of the invention and further objects, features and advantages thereof will be better understood from the following description taken in connection with the accompanying drawings in which:

The FIGURE illustrates somewhat schematically a withdrawal path for an ingot as it is being withdrawn and veered from the vertical to the horizontal after leaving a mold.

Proceeding to the detailed description of the drawing, there is provided a mold M having a particular curvature and from which is withdrawn an ingot S. The cross-sectional view of the drawing shows the growth in the solidified skin Ss and the reduction in the cross-sectional dimension of the still liquidous core S1.

The ingot leaves the mold in curved configuration with a particular radius, and guide rolls such as 1 are disposed to support and to guide the ingot along a correspondingly curved path. Point A is a first bending point for the ingot to increase the radius of curvature, point B is a second bending point for further increasing the radius of curvature of the ingot, and at bending point C the ingot has been straightened. Rolls on the inside of the curved path guide and support the ingot from above, rolls on the outside path provide also for support, from below of the ingot.

The drawing is schematic but it can be seen that in accordance with reality some of the steel is still liquidous beyond bending point C from where the ingot proceeds horizontally. The guiding and driving of ingot S for purposes of its withdrawal, therefore, does in fact require engagement between driven rolls and skin Ss of the ingot at those portions where there is still a liquidous core S1. Also, the schematic showing of the drawing clearly illustrates that in the first portion of the veering path the solidified skin is quite thin.

Many of the rolls 1 as illustrated, are merely guide rolls and are not driven; those that are driven are collectively marked, and they are individually designated by reference numerals 2 through 12. The reason for eleven driven rolls is based on a particular case and is representative only. in the particular example it is assumed that the torques of the driven rolls 2 12 are all similar, and that the driven rolls have similar diameter. Therefore, the forces imparted by the several rolls upon the casting ingot, are similar. It may be assumed further that the total force needed to drive the ingot for purposes of its withdrawal is about-88 metric tons. Finally, it is assumed that each rollis urged against the ingot at a contact pressure force that is the L3 fold value of the particular ferro-static load as effective-in the particular point of the ingot so engaged. It will be noted that rolls 4, 10, 11 and 12 engage the ingot in places where having solidified throughout. For these rolls, therefore, there is the rule that their contact pressure force is to be equal to the contact pressure force provided by the last one of the rolls that acts upon a portion of the ingot where there is still some non- "means of springs (not shown).

On basis of these values, the total number of rolls to be driven is eleven, and these are the driven rolls 2 12. This holds true essentially independently from the distribution of the particular locations of the driven rolls along the withdrawal path. The invention now concerns particular rules for such a distribution. The ratio of the total driving forces imparted by rolls upon the upper side of the ingot, along the inside of the curved path, and of the total of the driving forces imparted by other rolls upon the lower side along the outer path, is to be within the range of 0.1 to 0.5, for example, three-eighth. This requires eight driven rolls (rolls 5 through 12) to be disposed along the lower side of the ingot, while three rolls, namely rolls 2, 3 and 4, are disposed on the upper side of the ingot. As stated, this particular distribution is based on the assumption that all rolls provide similar torques, have similar diameters, and, therefore, provide similar driving forces. This, however, does not preclude that their torques do, in fact, differ, and that there is a variable torque distribution in longitudinal direction along the travel path of the ingot, in a known manner. The sum total of the driving forces acting on the upper side and the sum total of the driving forces acting on the lower side and/or their particular ratio relation can readily be maintained, or varied within the stated range, on basis of such unequal distribution of torque in longitudinal direction. I

It is of advantage for practicing the invention, by proportioning and distributing the several driven rolls in accordance with the stated rule, to'have at least one roll disposed on the inside of the curved path before the first bending point(A in the particular illustrated example, this-is roll number 2. Moreover, this roll 2 should be driven with the highest torque in the drive system.

In cases such as here, where there are several bending points provided, it is of advantage to have one driven roll Positioned in each bending point on the outs de path 0 the ingot; in the particular illustrated example these are rolls 5, 7 and 9. The provision of rolls in these points is well possible within the distribution pattern of driven rolls called for in accordance with this invention.

The invention is not limited to the embodiments described above but all' changes and modifications thereof not constituting departures from the spirit and scope of the invention are intended to be included.

I claim:

1. In a method for withdrawing a continuously cast steel ingot from a mold along a curved withdrawal path, there being support and guiding rolls provided for engagement with the ingot along that path, some of these rolls being driven, the improvement comprising the step of proportioning the driving forces as imparted by the rolls upon the ingot so that the ratio of the sum of the driving forces imparted by the driven rolls upon the upper side of the ingot to the sum of the driving forces imparted by the driven rolls upon the lower side of the ingot to be within the range of about 0.1 to 0.5.

2. Method in accordance with claim 1, with straightening of the ingot along the path, there being at least one bending point, and including the step of placing one of the driven rolls on the upper side of the ingot to be located before the first bending point for the inget.

3. Method in accordance with claim 2 and including the step that the torque for the latter roll is proportioned to be higher than the torque for any of the other rolls along the ingot withdrawal path.

4. Method as in claim 1, with straightening of the ingot along the withdrawal path by operation of several bending points, including the step of providing a driven roll on the lower side of the ingot in each bending point.

5. Method as in claim 1, including the step of using a contact pressure force for the driven rolls of about 1 to 1.5' the ferrostatic pressure and providing a larger number of driven rolls on the lower side than on the upper side. 

1. In a method for withdrawing a continuously cast steel ingot from a mold along a curved withdrawal path, there being support and guiding rolls provided for engagement with the ingot along that path, some of these rolls being driven, the improvement comprising the step of proportioning the driving forces as imparted by the rolls upon the ingot so that the ratio of the sum of the driving forces imparted by the driven rolls upon the upper side of the ingot to the sum of the driving forces imparted by the driven rolls upon the lower side of the ingot to be within the range of about 0.1 to 0.5.
 2. Method in accordance with claim 1, with straightening of the ingot along the path, there being at least one bending point, and including the step of placing one of the driven rolls on the upper side of the ingot to be located before the first bending point for the ingot.
 3. Method in accordance with claim 2 and including the step that the torque for the latter roll is proportioned to be higher than the torque for any of the other rolls along the ingot withdrawal path.
 4. Method as in claim 1, with straightening of the ingot along the withdrawal path by operation of several bending points, including the step of providing a driven roll on the lower side of the ingot in each bending point.
 5. Method as in claim 1, including the step of using a contact pressure force for the driven rolls of about 1 to 1.5 the ferrostatic pressure and providing a larger number of driven rolls on the lower side than on the upper side. 